JPH02228300A - Method and apparatus for voltage regulation of power source - Google Patents

Abstract

PURPOSE: To correctly adjust the output voltage of a power source by coupling the first and second control signals to a connecting point through an OR circuit, generating the output signals at the connecting points, and controlling the output voltage of the power source, in response to the output signals. CONSTITUTION: A voltage regulator 36 monitors the output voltages of an inverter 26 through lines 38, 40 and 42. The output currents of the inverter 26 are sensed by current transformers 44, 46 and 48. The exciting field current of a generator 10 is controlled through a line 60 by using all the inputs. That it to say, the bias voltage signal is supplied to the connecting point, and the first and second control signals are coupled to the connecting point through an OR circuit. Thus, the output signal is generated at the connecting point. The output voltage of the power source is controlled, in response to this output voltage. Thus, the sensing and control of the generator output voltage for optimizing the system performance can be performed with the excitation of the generator 10 being controlled by using the linear-error output signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to voltage regulation circuits and methods, and more particularly to such circuits and methods utilized in regulating the output voltage of a power source.

A typical generator voltage regulator has a sensing circuit that senses a high power AC or DC output voltage from the generator and generates a DC output signal that is proportional to the sensed voltage. The output signal of the sensing circuit is subtracted from the reference signal to generate an error signal proportional to the difference between the generator's actual output and the desired output. A compensation circuit changes the loop gain of the voltage regulator feedback control loop to obtain the desired transient response.

The output of the compensation circuit is amplified to generate the exciter field current of the generator.The output of the generator is proportional to the exciter field current. Due to the high power levels required, typically
A switching amplifier is commonly used to generate the exciter field current. These amplifiers require a pulse width modulated input, which is generated by amplifying the error signal.

However, the requirement for a pulse width modulated output from the error amplifier imposes various constraints on the sensing circuit. Since the gain of the error amplifier is determined by the ripple in the sensing circuit output, this ripple must be controlled to maintain constant system gain.

This constraint imposed on the sensing circuit can be avoided if the power amplifier of the regulator can operate with a linear error signal, thus eliminating the need for a pulse width modulated error signal.6 The present invention provides a linear error output Circuits and methods are provided for sensing and controlling generator output voltage to optimize system performance while controlling generator excitation using signals.

The present invention provides a method for regulating the output voltage of a power source, in which a first state signal representative of the output voltage of the power source is generated and combined with a reference signal to generate a first control signal. Similarly, a second state signal representative of the output current of the power source is generated and combined with the reference signal to generate a second control signal. supplying a bias voltage signal to the connection point;
An output signal is generated at the connection point by coupling the first and second control signals to the connection point via an OR circuit. The output voltage of the power supply is controlled in response to this output signal. The magnitude of the first control signal is greater than the bias voltage signal when the output voltage of the power source is less than a predetermined magnitude, and the magnitude of the second control signal is greater than the bias voltage signal when the output voltage of the power source is less than a predetermined magnitude. When it is small, it is larger than the bias voltage signal.

When the method of the present invention is used in a DC link variable speed constant frequency power generation system, another state signal representative of the DC voltage on the DC link conductor is generated and combined with the reference signal to generate a third control signal. This third control signal is also coupled to the node via an OR circuit. The magnitude of the third control signal is greater than the bias voltage signal when the second DC voltage is less than the second predetermined magnitude.

When the present invention is applied to a generator with a multi-phase output, another status signal is generated representing the magnitude of the output phase of the generator with the highest voltage. This further status signal is combined with the output current status signal to generate a second control signal.

The invention also includes circuitry for implementing the method described above. These circuits produce linear outputs and use separate error detectors to compensate the power source's output voltage and control the load current.

A circuit implementing the method of the invention is characterized by a soft start in that, when turned on, the reference signal is a DC voltage signal that gradually increases to a normal operating level.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail by way of embodiments with reference to the accompanying drawings.

Referring to the accompanying drawings, FIG. 1 is a block diagram of a power generation system with a voltage regulator for implementing the method of the present invention. This system requires an external prime mover (not shown)
line 1 coupled to be driven at variable speed by
2.14.16 has a generator 10 generating three-phase output. This three-phase output is rectified by a bridge rectifier 18 and sent to a pair of DC link conductors 20,22.

A filter capacitor 24 is connected between the DC link conductors. Inverter 26 receives the DC voltage from the DC link conductors and produces a constant frequency polyphase output on line 28.30.32.34.

The voltage regulator 36 of the present invention monitors the inverter output voltage via lines 38.40.42. The output current of the inverter is sensed by a current transformer 44.46.48 which generates a current signal on line 50.52.54. The regulator also monitors the DC link voltage via line 56.58 by a signal conditioning circuit 59 with a differential amplifier and filter. The voltage regulator uses all of this power to control the exciter field current of the generator 10 via line 60.

2A and 2B are circuit diagrams of the voltage regulator of FIG. 1; The voltage regulator has a voltage monitoring circuit 62, which connects the phase conductor 28.30.3 via resistors Ra, Rb%Rc.
2, and consists of diodes CRI, CR2, CR3, resistors R1, R2, R3, R4, and capacitor C1. These components cooperate to generate a first status signal on line 64 representing the average output voltage of the inverter appearing on lines 28, 30, 32. line 66
is connected to high voltage phase sensing circuit 68. The high voltage phase sensing circuit consists of diode CR5, amplifier Ut, resistors R8, R
Consists of 9.

These components cooperate to generate a state signal at the output of amplifier U1 that is proportional to the maximum voltage appearing on the output phase conductor of the inverter. Bridge type rectifier BRI, B
H2, BH3, diode CR6, CR7, CR8, C
R9, CRIO.

A current sensing circuit 72 consisting of CR11, resistors R11, R12, and R13 senses the generator output current through current transformers 44, 46, 48 and generates a status signal output representative of the inverter output current. These circuits 68, 72, capacitor C2, and resistor RIO together form a peak sensing circuit that generates a combined status signal on line 84.

The magnitude of the combined state signal is determined by the maximum of the phase current indication signal on line 70.71.74 and the high voltage phase state signal at the output of Ul.

A soft start reference circuit 76 controls system start-up. This circuit consists of transistor Q1, diode CRI 2, CR13, CR14, CR15, capacitor c3, C4, resistor R14, R15, R16, R17
, R18. With switch SWI in the closed position, these components operate to generate a DC reference voltage signal on line 78.

Amplifier U2, diode CR4, CRI 6, capacitors C5, C6, C7, resistors R5, R6, R7, R19,
Amplification and compensation circuit 80 consisting of R20, R21, and R22
combines the reference signal on line 78 and the first voltage state signal on line 64 to generate a first control signal on line 82.

The combined status signal on line 84 is sent to an amplification and compensation circuit 86. This circuit consists of amplifier U3, diode CRI
7, capacitors C8, C9, resistors R23, R24, R2
Consists of 5. These components operate to combine the reference signal on line 78 with the combined status signal on line 84 to generate a second control signal on line 88.

Terminal 90 is connected to the output of signal conditioning circuit 59 of the system of FIG. 1, and a voltage divider formed by resistors R26 and R27 is operative to produce a DC link voltage status signal on line 92 representative of the DC link voltage. do. Amplifier U4, diode CRI 8, capacitor Ct
O.

A third amplification and compensation circuit 94, consisting of C11, resistors R28, R29, and R30, receives the DC link voltage status signal and the reference signal and provides a third control signal on line 96 by combining and amplifying these signals. generate a signal.

By applying a DC voltage to the terminal 98, the resistor R31
A DC bias voltage is generated at connection point 100 via line 102 and line 102 . Diode CR19, CR20, CR
21 connects the control signal on line 82.88.96 to connection point 1
The output signal produced by this configuration acts as an OR circuit that couples to
is sent to the power amplifier 106 via. A power amplifier controls the generator exciter field current via line 108.

The operation of the circuit of FIGS. 2A and 2B will now be described. When switch S1 is in the closed position, transistor Q1 transfers the reference signal on line 78 to diodes CR12, CRI3,
Clamped to ground potential via resistor R15. When switch S1 opens to turn on the circuit, transistor Q1 turns off and charges capacitor C4 to a level of 15 volts. The reference voltage on line 78 ramps to a level determined by reference Zener diode CR4 and potentiometer Rf. In the preferred embodiment of the invention, the typical AC output voltage of the inverter is 115 volts three phase at 400 hertz. Three-phase AC voltage is sensed by resistor Ra.
%Rb%Rc. The half-wave current flows through these resistors and diodes CRI, CR2, CR3 to the resistor R.
Flows to 2. The resulting voltage waveform across resistor R2 appears to be a six-pulse full-wave rectified signal, but actually consists of the sum of three half-wave rectified input currents.

Therefore, the waveform at resistor R2 contains information about a complete positive half cycle of each phase voltage; thus, the response to changes in input voltage is very rapid. The voltage across resistor R2 is divided by resistors R1, R3, and R4 and filtered by capacitor C1 to remove high frequency noise. Resistor R1 has a positive temperature coefficient to compensate for the voltage across the input diode.

The voltage across capacitor C1 is compared to a reference voltage by amplification and compensation circuit 80. Input resistance R20 and feedback elements R, 19, C6, C7, CR16 are generator-
Vary the gain of the regulator to control the transient response of the system. The output of amplifier U2 is connected to pull-up resistor R31 via diode CR21.

The alternating current is sensed by current transformers coupled to the three output phases of the generator. Each phase current signal is rectified by a diode bridge and applied to a burden resistor and a diode to generate a voltage signal proportional to the alternating current of that phase. The three voltage signals are connected to diodes CR7, CR9, and C such that the entire current signal is generated across resistor RIO.
Connected via RI 1. Burden resistance R11, R12
, diodes CR6, ρR8, CR10 in series with R13
compensates for the voltage drop across diodes CR7, CR9, CRI1. Filter capacitor C2 provides a long discharge time constant so that the current sensing circuit responds to peak currents. This makes single-phase or three-phase current limiting performance almost equal. The voltage on line 84 is compared to a reference voltage by an amplification and compensation circuit 86. The output of circuit 86 is connected through diode CR20 to pull-up resistor R31.

When used in a DC link variable speed constant frequency system, there is a buffered DC link signal input 90. If the AC sensing circuit fails or the AC voltage is shorted, the DC input can be used to limit the link voltage. The voltage generated by voltage dividing resistors R26 and R27 is compared with a reference voltage by an amplification and compensation circuit 94. The output of this circuit 94 is connected to a pull-up resistor R31 via a diode CR19.

The AC sense voltage at resistor R2 is also connected to voltage divider resistor R8.
and R9, to amplifier U1. Amplifier U1 is connected to form a peak detector and charges capacitor C2. The voltage at C2 thus becomes responsive to the peak voltage of the maximum input AC voltage. Capacitor C2 is charged to a level slightly below the reference voltage for normal operation.

The voltage of pull-up resistor R31 is the same as that of resistor U2, U3 or U.
It is controlled by the lowest output of the four. When the control signal is off, the voltage across resistor R31 is pulled down to ground potential by transistor Q1 via diode CR22. Diode CR23 is diode C of the OR circuit
To compensate for the voltage drops across RI 9, CR20, and CR21, the circuit output matches the lowest controlled error amplifier output or goes to zero when transistor Q1 is on. The circuit output on line 104 is used to IIJall the generator exciter field current.

The feedback elements of the three amplifier and compensation circuits 80.86.94 are connected in slightly different ways. The output of each amplifier is clamped by a feedback diode that operates to maintain closed loop control of the amplifier that is not currently controlling the generator output. The feedback RC circuit of each amplifier is connected to the pull-up resistor side of the OR diode circuit. This connection maintains proper biasing on the feedback capacitors to ensure quick response of each control loop. If the feedback circuit of amplifier U2 were connected directly to its output, there would be a delay in the response of the voltage regulator. For example, during a short circuit, the AC sense voltage would be zero and the output of amplifier U2 in one embodiment would be approximately 5.6 volts DC. This difference will appear across capacitor C7 and should cause a delay in the response of amplifier U2 and start the voltage loop once the short condition is removed. Capacitor C6 between the input and output of amplifier υ2
reduces the ripple voltage in the output control signal without affecting the circuit response.

The feedback circuit between the input and output of the amplifier U4 is the amplifier U.
A capacitor C between the input and output of the amplifier U3 as in case 2, but without a direct feedback capacitor.
8 has a large capacitance and affects the transient response of the system. This is necessary because the high voltage phase sense signal from amplifier U1 biases the input of amplifier U3 very close to the reference level. Without capacitor C8, the response when a load is applied to the control circuit will be slower as the output of amplifier U3 attempts to control the rate of rise of the control signal.

From the foregoing, it is clear that a circuit constructed in accordance with the present invention includes circuits that separately sense the AC voltage and output current of the inverter. The output of each sensing circuit is compared to a reference signal by a separate error amplifier, and compensation is provided for each error amplifier.

The amplifier output is connected to a pull-up resistor via an OR circuit to generate the output of the control circuit. This output is amplified by a power amplifier to form the exciter field current of the generator.The individual error amplifiers may use a common reference signal or separate reference signals. good.

The ORing of the diodes forms a logic circuit to determine which circuit is controlling the exciter field current of the generator. Normally, an AC voltage sensing and error amplifier controls the current and DC current. The inputs are below the reference level and the outputs of their amplifiers are at a high level. When the load current exceeds the desired level, the output of error amplifier U3 goes low to control the power stage input and thus the generator exciter field current. The same effect occurs in amplifier U4 when the DC link voltage exceeds a set limit. The use of separate error amplifiers and compensation circuits optimizes the response to conventional AC regulation, current limiting and DC link voltage limiting.

AC voltage sensing circuit 62 is responsive to the average value of the three input phase voltages. High voltage phase sensing circuit 68 produces an output proportional to the magnitude of the maximum phase voltage. This is important in unbalanced load or overload situations where the average voltage is still regulated within normal limits, but the maximum phase voltage exceeds specifications. The output of the high voltage phase sensing circuit is combined with the output of the current sensing circuit, and the combined signals share the same error amplifier.

The voltage regulation of the present invention allows sensing and control with linear output signals. Independent error detectors and compensation circuits may be provided for each of AC control, load current control, and DC link control.

Due to the large gain of the error amplifier, adjustment is limited only by the accuracy of the sensing and reference voltages. AC sensing with rapid response characteristics and high voltage phase suppression are also features of the invention.

Although the present invention has been described in terms of the presently preferred embodiments, it will be apparent to those skilled in the art that various modifications and changes in design will occur to those skilled in the art without departing from the scope of the invention. Although the case where it is used for a power source having a polyphase alternator and an inverter has been explained,
A preferred embodiment of the present invention can also be used with other types of power sources; polyphase alternators, single-phase alternating current and direct current generators can be used alone or in combination with inverters. be. Accordingly, the appended claims are intended to encompass these systems as well.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a power generation system with a voltage regulator implementing the method of the invention. 2A and 2B are schematic diagrams of the voltage regulator of FIG. 1; 72...Current sensing circuit 76...Reference circuit 80.86.94...For amplification and compensation circuit Application agent: Westinckheuss Electric Corporation Person: Hiroshi Kato (one idiot) ... Generator ... Inverter ... Voltage regulator ... Differential amplifier and filter ... Voltage monitor circuit ... High voltage sensing circuit FIG, 1

Claims (6)

[Claims] (1) A method for adjusting an output voltage of a power source, the method comprising: generating a first status signal representing the output voltage of the power source;
A state signal is combined with a reference signal to generate a first control signal, a second state signal representative of the output current of the power source is generated, and a second state signal is combined with the reference signal to generate a second control signal. generating a control signal at the junction, providing a bias voltage signal to the junction, and coupling the first and second control signals to the junction via an OR circuit to generate an output signal at the junction; controlling the output voltage of the power source in response to the signal, the magnitude of the first control signal being greater than the bias voltage signal when the output voltage of the power source is less than a predetermined magnitude; the magnitude of the bias voltage signal is greater than the bias voltage signal when the output current of the power source is smaller than a predetermined magnitude. (2) A method for adjusting an output voltage of a power source, the method comprising: generating a first status signal representative of the output voltage of the power source;
a first control signal in combination with a state signal of the power source to generate a second state signal representative of the output current of the power source;
combine a state signal with the reference signal to generate a second control signal, generate a third state signal representative of a DC voltage obtained by rectifying the output voltage of the power source, and generate a third state signal. generating a third control signal in combination with the reference signal, providing a bias voltage signal to the node, and coupling the first, second and third control signals to the node through an OR circuit; generating an output signal at the connection point and controlling an output current of the power source in response to the output signal, the first control signal having a magnitude when the output voltage of the power source is less than a predetermined magnitude; is greater than the bias voltage signal, the magnitude of the second control signal is greater than the bias voltage signal when the output current of the power source is less than a predetermined magnitude, and the magnitude of the third control signal is greater than the magnitude of the DC voltage. An adjustment method characterized in that when the magnitude is smaller than a second predetermined magnitude, it is greater than the bias voltage signal. (3) A method for regulating the output voltage of a power source, the method comprising: generating a first state signal representative of the average output voltage of the multiphase power source; and combining the first state signal with a reference signal to adjust the output voltage of the power source. generating a control signal, generating a second state signal representative of a maximum voltage magnitude of a plurality of output phases of the power source, generating a third state signal representative of an output current of the power source; combining the three state signals to generate a fourth state signal; combining the fourth state signal with the reference signal to generate a second control signal; providing a bias voltage signal to the node; generating an output signal at the node by coupling the first and second control signals to the node through an OR circuit, and controlling the output current of the power source in response to the output signal; The magnitude of the second control signal is greater than the bias voltage signal when the output voltage of the power source is less than a predetermined magnitude, and the magnitude of the second control signal is greater than the bias voltage signal when the output current of the power source is less than the predetermined magnitude and the power A method of regulation characterized in that the magnitude of the maximum voltage of the output phase of the source is greater than the bias voltage signal when it is less than a second predetermined magnitude. (4) means for generating a first state signal representative of the output voltage of the power source;
means for generating a control signal of the power source; means for generating a second status signal representative of the output current of the power source; and means for combining the second status signal with the reference signal to generate a second control signal. , means for providing a bias voltage signal to the node;
and an OR circuit for generating an output signal at the connection point by coupling a second control signal to the connection point;
The magnitude of the first control signal is greater than the bias voltage signal when the output voltage of the power source is less than a predetermined magnitude, and the magnitude of the second control signal is greater than the bias voltage signal when the output voltage of the power source is less than a predetermined magnitude. A sensing/control circuit for a voltage regulator characterized in that when it is small, it is larger than a bias voltage signal. (5) means for generating a first state signal representative of the output voltage of the power source;
means for generating a control signal of the power source; means for generating a second status signal representative of the output current of the power source; and means for combining the second status signal with the reference signal to generate a second control signal. , means for generating a third state signal representative of a direct current voltage obtained by rectifying the output voltage of the power source, and means for combining the second state signal with the reference signal to generate a third control signal. a means for supplying a bias voltage signal to the connection point; and an OR circuit for coupling the first, second and third control signals to the connection point to generate an output signal at the connection point; The magnitude of the first control signal is greater than the bias voltage signal when the output voltage of the power source is smaller than a predetermined magnitude, and the magnitude of the second control signal is greater than the bias voltage signal when the output current of the power source is smaller than the predetermined magnitude. When the magnitude of the third control signal is greater than the bias voltage signal, the magnitude of the third control signal is such that the DC voltage is greater than the second
A sensing/control circuit for a voltage regulator, wherein the sensing/control circuit is greater than a bias voltage signal when less than a predetermined magnitude of the bias voltage signal. (6) means for generating a first state signal representative of the average output voltage of the multiphase power source; and means for combining the first state signal with a reference signal to generate a first control signal; means for generating a second status signal representative of the maximum voltage of the plurality of output phases; means for generating a third status signal representative of the output current of the power source; and converting the second status signal into a third status signal. means for combining to generate a fourth status signal; means for combining the fourth status signal with the reference signal to generate a second control signal; and means for providing a bias voltage signal to the node; 1st
and an OR circuit that generates an output signal at the connection point by coupling a second control signal to the connection point,
The magnitude of the first control signal is greater than the bias voltage signal when the output voltage of the power source is less than a predetermined magnitude, and the magnitude of the second control signal is greater than the bias voltage signal when the output voltage of the power source is less than a predetermined magnitude. A sensing/control circuit for a voltage regulator characterized in that the bias voltage signal is small and greater than a bias voltage signal when the maximum voltage on the output phase of the power source is less than a second predetermined magnitude.